package com.itcag.util.txt;

final class LevenshteinDistance {

    protected final static int LevenshteinDistance (String s0, String s1) {

        int len0 = s0.length() + 1;
        int len1 = s1.length() + 1;

        // the array of distances
        int[] cost = new int[len0];
        int[] newcost = new int[len0];

        // initial cost of skipping prefix in String s0
        for (int i = 0; i < len0; i++) cost[i] = i;

        // dynamicaly computing the array of distances

        // transformation cost for each letter in s1
        for (int j = 1; j < len1; j++) {
            // initial cost of skipping prefix in String s1
            newcost[0] = j;

            // transformation cost for each letter in s0
            for(int i = 1; i < len0; i++) {
                // matching current letters in both strings
                int match = (s0.charAt(i - 1) == s1.charAt(j - 1)) ? 0 : 1;

                // computing cost for each transformation
                int cost_replace = cost[i - 1] + match;
                int cost_insert  = cost[i] + 1;
                int cost_delete  = newcost[i - 1] + 1;

                // keep minimum cost
                newcost[i] = Math.min(Math.min(cost_insert, cost_delete), cost_replace);
            }

            // swap cost/newcost arrays
            int[] swap = cost; cost = newcost; newcost = swap;

        }

        // the distance is the cost for transforming all letters in both strings
        return cost[len0 - 1];

    }

}
